The present invention is generally directed to an electronic document detector and in particular to an electronic document detector for use in a document recorder or similar environments.
Document recorders are well known in the art and find considerable use in applications where it is desirable to make a permanent record of a series of documents on microfilm. For example, such a device finds considerable use in banking systems wherein cancelled checks are permanently recorded on microfilm. While making the permanent record of the checks on microfilm, it is desirable to be able to count each document so that the total number of documents recorded may be obtained. In providing this function document recorders have generally included document detecting systems which detect the presence of each document as they enter the recording device.
While document detecting systems of the prior art have been successful to some degree, they have suffered from a number of deficiencies. First, many document detectors include a light source and a photocell having a relatively small light detecting area. With the growing popularity of computers, and particularly computer processing of checks, many checks which are to be recorded will include areas having a number of computer punch holes in them. The individual computer punch holes are on the same order of magnitude in dimensions as the effective light detecting area of the photocells and thus a document having such computer punch holes may cause a document detecting system of the prior art to detect and count the same document twice. This problem may also occur when a document to be detected has binder holes along its margin.
Another problem has been that through age, the light sources will experience a degradation in their light output and thus upset the required voltage or current transitions which must take place in order for the document detecting systems to operate properly. In addition, such systems also will accumulate dirt on the light sources and various other system elements. The accumulation of dirt will have the same effect on the system as the light output degredation of the light sources.
It is therefore a general object of the present invention to provide a new and improved electronic document detector.
It is a further object of the present invention to provide an electronic document detector with increased dynamic range to thereby obtain the necessary current and voltage transitions required for proper functioning not withstanding aging of the detector or the accumulation of dirt within the detector.
It is a still further object of the present invention to provide a new and improved electronic document detector which is capable of properly identifying documents having punched holes to thereby maintain a high degree of accuracy and integrity in the document detection.